Search

Your search keyword '"Scarpa, Fabrizio"' showing total 992 results
Start Over Author "Scarpa, Fabrizio"
992 results on '"Scarpa, Fabrizio"'

3. Acoustic Transmission Loss in Hilbert Fractal Metamaterials

Author

Comandini, Gianni, Ouisse, Morvan, Ting, Valeska P., and Scarpa, Fabrizio

Subjects
Physics - Applied Physics
Abstract

Acoustic metamaterials are increasingly being considered as a viable technology for sound insulation. Fractal patterns constitute a potentially groundbreaking architecture for acoustic metamaterials. We describe in this work the behaviour of the transmission loss of Hilbert fractal metamaterials used for sound control purposes. The transmission loss of 3D printed metamaterials with Hilbert fractal patterns related to configurations from the zeroth to the fourth order is investigated here using impedance tube tests and Finite Element models. We evaluate, in particular, the impact of the equivalent porosity and the relative size of the cavity of the fractal pattern versus the overall dimensions of the metamaterial unit. We also provide an analytical formulation that relates the acoustic cavity resonances in the fractal patterns and the frequencies associated with the maxima of the transmission losses, providing opportunities to tune the sound insulation properties through control of the fractal architecture., Comment: Submitted to Scientific Reports

Published
2023

5. Large Impact of Small Vertex Cuts on the Mechanics of Origami Bellows

Author

Yang, Mengzhu, Grey, Steven W., Scarpa, Fabrizio, and Schenk, Mark

Subjects
Physics - Applied Physics
Abstract

For origami structures, perforating or cutting slits along creases is an effective method to define fold lines and alleviate stress concentrations at vertices. In this letter we show numerically and experimentally that for non-rigid-foldable origami bellows (e.g. Miura-ori, Kresling patterns) the introduction of small cut-outs at the vertices results in up to an order of magnitude reduction of the bellows' stiffness under axial compression. Further, the cut-outs at vertices impact the nonlinear response, e.g. the position and magnitude of a force limit point and presence of bistable configurations. As the origami bellows are not rigid foldable, an axial compression will necessarily result in facet deformations; the small cut-outs at the vertices are found to provide an unexpectedly large stress alleviation, resulting in disproportionate changes in mechanical properties of the bellows. In order to accurately model the mechanics of origami bellows, such manufacturing details must therefore be captured accurately. Lastly, introducing vertex cut-outs can be offered as a novel approach to tailoring the stiffness of non-rigid foldable origami structures.

Published
2022

13. Water aging effects on the flexural properties of fully biobased coir fiber composites

Author

Assis, Eduardo Geraldo, dos Santos, Julio Cesar, da Silva, Rodrigo Jose, de Oliveira, Livia Avila, del Pino, Gilberto Garcia, Scarpa, Fabrizio, and Panzera, Tulio Hallak

Subjects
Castor oil -- Analysis, Humidity -- Analysis, Polymers -- Analysis, Engineering and manufacturing industries, Science and technology
Abstract

This work describes the flexural behavior of biocomposites composed of a polyurethane matrix derived from castor oil plants and coir fibers. A statistical design is performed to identify the effects of fiber alkaline treatment and aging on the flexural modulus and strength of the composites. Physical tests and failure analyses are carried out to better assess their mechanical performance. A second experiment at 100% relative humidity is performed on treated fiber composites to compare with those obtained by immersion in water. The flexural modulus of the composites is not significantly affected by the fiber alkali treatment, while the strength is reduced by 35.17% when treated fibers are considered. Increasing the exposure time of composites under both aging conditions progressively reduces their flexural properties. The aging process of biocomposites in an environment with 100% relative humidity takes twice as long to reduce to the same flexural properties as those aged in water. Highlights * Composites made with treated fibers showed higher apparent density and lower porosity. * Water aging reduces flexural modulus and strength of biobased coir composites. * The bending properties are strongly dominated by the properties of biobased polymer. * 100% relative humidity takes twice as long to reduce to the flexural properties as those aged in water. * Untreated coir fibers achieve superior bending properties under moisture aging. KEYWORDS aging process, alkaline treatment, biobased polyurethane, coir fiber, flexural properties, 1 | INTRODUCTION In recent years, the increase in nondegradable waste accumulated in landfills, mainly polymeric materials derived from petroleum, has generated considerable environmental problems. (1) For this reason, the [...]

Published
2023
Full Text
View/download PDF

18. Sound absorption in Hilbert Fractal and Coiled Acoustic Metamaterials

Author

Comandini, Gianni, Khodr, Codor, Ting, Valeska, Azarpeyvand, Mahdi, and Scarpa, Fabrizio

Subjects
Physics - Applied Physics
Abstract

We describe here a class of acoustic metamaterials with fractal Hilbert space-filling and coiled geometry with equal tortuosity for noise mitigation. Experiments are performed using a four-microphone impedance tube and benchmarked against non-viscous and viscothermal Finite Element models related to configurations spanning up to five fractal/geometry orders. We show that the acoustic absorption can be predicted by the resonance of the cavities associated to the tortuous paths. For a given fractal/geometry order, the acoustic absorption at specific frequencies is also enhanced by maximising the difference between the minimum and maximum fluid particle velocity of the air inside the patterns. These principles can be used to design high-performance acoustic metamaterials for sound absorption over broad frequency ranges., Comment: 4 pages, 3 figures, Submitted to Applied Physics Letters

Published
2021
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results